In recent years, color devices such as monitors, printers, and the like have prevailed, and the color management technique that manages color information is increasing in importance. Since display devices such as monitors and the like have different color gamuts from output devices such as printers and the like, color information of display devices cannot be handled as that of output devices intact. Hence, a color management system (to be referred to as a “CMS” hereinafter) becomes important. This system temporarily converts color information of an image input device into that in the absolute color space, and then converts the information in the absolute color space into that in a color space of an image output device, so as to convert and output color data of the image input device into color data that can be reproduced by the image output device.
FIG. 1 is a chart showing the flow of the processes of the CMS executed when an image input by an input device is to be output by an output device.
An input color space 201 which depends on an input device such as a digital camera, scanner, or the like is converted into an absolute color space 203 by a source profile 202. The absolute color space 203 is converted into an output color space 205, which depends on an output device, by a destination profile 204. Note that the source profile 202 is used to convert the input color space into the absolute color space, and the destination profile 204 is used to convert the absolute color space into the output color space. As these profiles, ICC profiles as the format specified by International Color Consortium (ICC) are popularly used nowadays.
FIGS. 2A and 2B show an example of the data expression formats of ICC profiles. Profiles used in a printer often expresses color space conversions using lookup tables (to be referred to as “LUTs” hereinafter), as shown in FIGS. 2A and 2B. FIG. 2A shows an LUT used to convert device-dependent CMYK data into device-independent Lab data, and FIG. 2B shows an LUT used to convert device-independent Lab data into device-dependent CMYK data.
The ICC profiles are normally distributed upon delivery of products of devices, or are installed in devices. However, every devices inevitably suffer characteristic variations due to aging, and default ICC profiles are not always optimal to devices whose characteristics have varied. Also, even when identical profiles are used in identical devices, images with the same tint are not always obtained depending on individual differences of the devices. A state wherein a plurality of devices have different tints especially poses a problem in a cluster printer environment in which identical images are distributed to and output by a plurality of printers. This is because when identical images are output using printers of the same type, images with the same tint are expected to be obtained.
In order to cope with such problems of aging and individual differences of devices, when ICC profiles are re-generated at a given timing or for each individual device, optimal color reproduction can be obtained at that timing or for that device.
However, many ICC profile generation tools print and measure a large number of color patches (in general, about 1,000 patches) and then make profile generation calculations. Hence, profile re-generation requires a long time. Furthermore, when a series of operations, i.e., print, colorimetry, and calculations are made in correspondence with a plurality of devices, a longer time is required. For this reason, it is difficult for devices whose device characteristics readily vary day by day such as electrophotographic color printers and the like to routinely re-generate profiles.